Transducer for converting acoustic vibrations into electrical oscillations, and vice versa, in the form of a diaphragm coated with at least one layer of a piezo-electric material

ABSTRACT

A microphone that includes a housing in which a flexible diaphragm comprising at least one layer of piezoelectric material is secured by means of a resilient ring surrounding the periphery of the diaphragm. A flat disc composed of an acoustic damping material is mounted directly on the center of the diaphragm by means of an adhesive substance.

United States Patent Roos [54] TRANSDUCER FOR CONVERTING ACOUSTIC VIBRATIONS INTO ELECTRICAL OSCILLATIONS, AND VICE VERSA, IN THE FORM OF A DIAPHRAGM COATED WITH AT LEAST ONE LAYER OF A PIEZO- ELECTRIC MATERIAL [72] Inventor: Jan Roos, Emmasingel,

Netherlands [73] Assignee: U.S. Philips Corporation, New York, NY.

[22] Filed: Sept. 25, 1969 [21] Appl. No.: 861,028

Eindhoven,

[30] Foreign Application Priority Data Sept. 30, 1968 Netherlands ..6813996 US. Cl. ..179/l10 A, 179/180 ..H04r 17/02 FieldofSearch ..l79/1l0A,180;310/8.3,9.1;

[451 Apr. 4, 1972 Harris, Handbook of Noise Control, 1957 pp. 13- 21- 22.

Primary Examiner-Kathleen H. Clatfy Assistant Examiner-Thomas L. Kundert Attorney-Frank R. Trifari 57 ABSTRACT A microphone that includes a housing in which a flexible diaphragm comprising at least one layer of piezoelectric material is secured by means of a resilient ring surrounding the periphery of the diaphragm. A flat disc composed of an acoustic damping material is mounted directly on the center of the diaphragm by means of an adhesive substance.

3 Claims, 5 Drawing Figures PATENTEDAPR 4 I972 3,654,402

fig.5

INVENTOR.

JAN ROOS BY LA 6.

TRANSDUCER FOR CONVERTING ACOUSTIC VIBRATIONS INTO ELECTRICAL OSCILLATIONS, AND VICE VERSA, IN THE FORM OF A DIAPHRAGM COATED WITH AT LEAST ONE LAYER OF A PIEZO-ELECTRIC MATERIAL The present invention relates to a microphone provided with a transducer for convening acoustic vibrations into electric oscillations in the fonn of a diaphragm coated with at least one layer of a piezo-electric material and a damping member for the vibrating plate.

Such a microphone is known in which the damping member is a magnetic member which forms part of a magnetic securing device, i.e. a magnet external to the transducer attracts the transducer inside the microphone casing and at the same time secures it.

The invention is characterized in that the clamping member is provided directly on the diaphragm. Compared with the known microphone this provides the advantage that the damping member is independent of the device for securing the diaphragm. Preferably the damping member is located at the area of the largest deflection of the diaphragm resulting in optimum damping thereof.

An embodiment of the invention is characterized in that at least part of the damping member is flat and that the member is secured throughout the area of this flat part.

A modification of this embodiment has a damping member which comprises a disc composed of a synthetic material having a high acoustic damping coefficient, preferably butyl rubber, which is provided flat on the diaphragm. The securing may simply be effected by means of an adhesive.

Another modification is characterized in that the component secured to the diaphragm is provided with several lugs which extend parallel to the diaphragm. In this embodiment, damping is caused by the volume displacement of the air in the gaps between the lugs and the diaphragm. Heavier damping is obtained by shaping the lugs so that together they form a dishshaped edge. This dampping can be further increased by providing the edges with corrugations.

The invention will be described more fully with reference to the drawing in which:

FIG. 1 is a cross-sectional view of a piezo-electric diaphragm provided with damping in accordance with the invention,

FIG. 2 is a plan view thereof,

FIG. 3 is a cross-sectional view of another embodiment of the invention, and

FIGS. 4 and 5 show plan views of the embodiment of FIG. 3 provided with lug-shaped and dish-shaped damping members, respectively.

FIG. 1 shows part of a microphone in which a transducer 1, which comprises two piezo-electric layers 2 and 3 each provided with an electrode 4 deposited from vapor, is clamped in a fixed part of a microphone casing 6 by means of a resilient ring made of Araldite. A disc of butyl rubber 10 is cemented centrally of the diaphragm 1.

In FIG. 3 the diaphragm 1 is also resiliently secured in a microphone casing 6. The damping member 10 comprises a central portion 11 which is secured to the diaphragm 1 by means of an adhesive 12. The damping elements of the damping member 10 are constituted by wing-shaped edge 13, which may take the form of lugs 14 (FIG. 4) or may be continuous and shaped in the form of a dish (FIG. 5). The dish-shaped edge may be provided with corrugations. The material used preferably is brass sheet.

What is claimed is:

A microphone comprising, a housing, a transducer for convetting acoustic vibrations into electric oscillations mounted within said housing, said transducer comprising a flexible diaphragm comprising at least one layer of piezoelectric material having an area of maximum deflection, and a damping member directly mounted on the diaphragm at said area of maximum deflection thereof at least a part of the damping member being flat and being secured to the diaphragm throughout said flat area, said damping member further comprising several lugs which extend from said flat part substantially parallel to and spaced apart from the diaphragm.

2. A microphone comprising,

a housing, a transducer for converting acoustic vibrations into electric oscillations mounted within said housing, said transducer comprising a flexible diaphragm comprising at least one layer of piezoelectric material having an area of maximum deflection, and a damping member directly mounted on the diaphragm at said area of maximum deflection thereof, at least a part of the damping member being flat and being secured to the diaphragm throughout said flat area, said damping member further comprising a peripheral portion extending from said flat part to form a dish-shaped edge that is spaced apart from the diaphragm.

3. A microphone as claimed in claim 2, characterized in that the edge is provided with corrugations. 

1. A microphone comprising, a housing, a transducer for converting acoustic vibrations into electric oscillations mounted within said housing, said transducer comprising a flexible diaphragm comprising at least one layer of piezoelectric material having an area of maximum deflection, and a damping member directly mounted on the diaphragm at said area of maximum deflection thereof, at least a part of the damping member being flat and being secured to the diaphragm throughout said flat area, said damping member further comprising several lugs which extend from said flat part substantially parallel to and spaced apart from the diaphragm.
 2. A microphone comprising, a housing, a transducer for converting acoustic vibrations into electric oscillations mounted within said housing, said transducer comprising a flexible diaphragm comprising at least one layer of piezoelectric material having an area of maximum deflection, and a damping member directly mounted on the diaphragm at said area of maximum deflection thereof, at least a part of the damping member being flat and being secured to the diaphragm throughout said flat area, said damping member further comprising a peripheral portion extending from said flat part to form a dish-shaped edge that is spaced apart from the diaphragm.
 3. A microphone as claimed in claim 2, characterized in that the edge is provided with corrugations. 